The present invention concerns a multi-function contact clamp made in a single piece of simple and economic design which acts like a key to prevent the push-button being removed once it has been set in place, like a return spring in a neutral position and like contact means for example on a printed circuit contact pad.
The invention also concerns a contact device wherein several clamps of the preceding type are positioned end-to-end.
Such a clamp, or contact device, finds application in very varied fields, more particularly in the control of electronic apparatus of small dimensions, such as timepiece parts.
In push-button devices, the use of flexible elements is already known for fulfilling certain key/return spring/contact means functions, given that it is desirable for the contact force to be less than the force having to be exerted on the push-button head, in particular when said contact is established on a printed circuit contact pad.
In Swiss Patent No. 621 034, a control mechanism for a watch movement includes a wire spring which is positioned between two supports arranged on either side of the push-button stem and whose median portion is engaged in a groove of said stem, thus fulfilling the dual role of key and return spring, the contact as such being assured by the action of the end of the push-button on a tilting strip.
In U.S. Pat. No. 4,818,830, a push-button mechanism is made by means of a flat metal spring cut along a complex substantially U-shaped contour and being secured and/or guided by several studs secured to the plate, so that one of the branches has sufficient flexibility to close a contact when force is exerted thereon via the end of the push-button stem. This mechanism thus fulfils the return spring and contact means functions but has no key function.
The mechanism proposed in British Patent No. 2 040 517 is formed by a pre-cut metal strip which includes a certain number of folds outside its general plane parallel to the plate. The strip is secured at one of its ends by a bent portion anchored in the plate and by a stud secured to the plate. On the push-button stem, and close to its end, the strip has a step bringing its plane below the general plane of the plate in a recess made for this purpose. This end includes, on the one hand, an opening, one edge of which is engaged in a groove of the push-button stem to form the key and return spring, and on the other hand, a rigid lug, bent towards the exterior of the plate and located along the axis of the push-button stem to form the contact on an elastic strip located opposite. A rigid tip extending beyond the stem comes abuts to a stop against one edge of the opening to position the push-button properly and wind the strip which forms the spring. This construction enables the spring/key/contact functions to be assured by a single strip, but it will be noted on the one hand, that not only does a trip have to be shaped, but hollow deformations have to be provided in the plate, and on the other hand that the force exerted on the push-button head is directly applied at the point of contact which can consequently only be formed by a strip spring.
The object of the invention is to overcome the drawbacks of the aforecited prior art by providing a contact clamp formed by a metal strip which is cut and bent to assure at least the spring, key and contact functions, while further allowing a smaller contact force to be obtained than the force which has to be exerted on the push-button head.
The invention therefore concerns a multi-function contact clamp associated with at least one push-button having a head and a stem passing through the middle part of a case closed by at least a back cover and including a plate and a metal grid, characterised in that said clamp is formed of a single part including a plane metal base substantially parallel to the back cover and provided with means for immobilising it in the case on one side of the stem and at least one elastic strip substantially perpendicular to the base, extending beyond the stem following a portion of the inner periphery of the middle part, said strip having opposite the stem a first prestressed portion having a notch co-operating with a groove arranged close to the end of the stem to form the key and return spring in the idle position, and a second portion having greater flexibility than the first portion, the end of which closes a contact of a printed circuit with less force than that which is necessary to activate the push-button.
In the event that the case is provided with several push-buttons, for example when the case is that of a chronograph watch, contact clamps of the preceding type may be arranged facing each push-button. According to an advantageous embodiment, the bases of each contact clamp are positioned end-to-end to form a single base along the periphery of the middle part including a plurality of flexible strips.